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Sea Stars and Sea Urchins

Two Examples of Echinoderms

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Northern Sea Stars and Green Sea Urchins / Blue Ocean Society

Northern sea stars can be many colors, as shown here in this image of Northern sea stars with another echinoderm, the green sea urchin.

© Blue Ocean Society

Sea stars, sand dollars, sea cucumbers and sea urchins are all echinoderms. Echinoderms exhibit radial symmetry. One characteristic of echinoderms is that while they have a top and bottom, they don't really have a right or left side.

The most obvious characteristic of sea stars are their arms. Depending on the species, sea stars usually have between 5 and 40 arms. All northern sea stars have 5 arms.

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